Hello,
So Y variable is what you would start with.
20 <= he'll start off with for a
40 <= what he'll start off with for b
And X variables would be the # of hours you're working.
10 <= meaning every hour worked is worth 10 dollars
5 <= meaning every hour worked will be paid 5 dollars
So let's just say for option a he works two hours
(Option A)
10 (2) + 20
20 + 20
= 40
(Option B)
5 (2) + 40
10 + 40
50
As for your equations
Y = 10x + 40
Y= 5x + 40